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<!--
This file is Copyright (c) 2018 by the GPSD project
SPDX-License-Identifier: BSD-2-clause
--><refentry id="gpsrinex.1">
  <refentryinfo>
    <date>09 Nov 2018</date>
  </refentryinfo>
  <refmeta>
    <refentrytitle>gpsrinex</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo class="source">The GPSD Project</refmiscinfo>
    <refmiscinfo class="manual">GPSD Documentation</refmiscinfo>
  </refmeta>
  <refnamediv id="name">
    <refname>gpsrinex</refname>
    <refpurpose>Read data from gpsd convert to RINEX3 and save to a file.</refpurpose>
  </refnamediv>
  <refsynopsisdiv id="synopsis">
    <cmdsynopsis>
      <command>gpsrinex</command>
      <arg choice="opt">-D <replaceable>debuglevel</replaceable></arg>
      <arg choice="opt">-f <replaceable>filename</replaceable></arg>
      <arg choice="opt">-h</arg>
      <arg choice="opt">-i <replaceable>interval</replaceable></arg>
      <arg choice="opt">-n <replaceable>count</replaceable></arg>
      <arg choice="opt">-V</arg>
      <group>
        <replaceable>server</replaceable>
        <group>
          <replaceable>:port</replaceable>
          <group>
            <replaceable>:device</replaceable>
          </group>
        </group>
      </group>
    </cmdsynopsis>
  </refsynopsisdiv>
  <refsect1 id="description">
    <title>DESCRIPTION</title>
    <para>
      <application>gpsrinex</application> is a tool to connect to
<application>gpsd</application> and output the received raw measurements
as a RINEX 3 observation file.  This is useful for sending raw measurements
(pseudorange and carrierphase) from <application>gpsd</application> to
a Precise Point Positioning (PPP) program or service.</para>
    <para>
      <application>gpsrinex</application> does not require root
privileges, and can be run concurrently with other tools connecting
to a local or remote <application>gpsd</application> without causing
problems.</para>
    <para>gpsrinex needs the GPS receiver to be sending raw measurements
to <application>gpsd</application>.  Only a few GPS have this capability.
In addition, the <application>gpsd</application> driver for that GPS
must support raw mode.  Currently only the u-blox driver has this support.
Only a few u-blox 8 GPS implment the required UBX-RXM-RAWX message.  The
NEO-M8T is known to work, but requires configuration with
<application>ubxtool</application>.</para>
    <para>RINEX has its own definitions and abbreviations.  Be
sure to consult their documentation.  An observation file (.obs)
contains data sets, called epochs, that contain the pseudorange
and carrierphase for each satellite seen.</para>
    <para>
      <application>gpsrinex</application> by default will acquire
20 epochs spaced apart by 30 seconds.  That will take 10 minutes to
complete.  Most users consider the 30 second interval to be optimal.
Many PPP programs require at least 1 or 2 hours data, but no more than
24 or 48 hours of data.  Most users consider 4 to 6 hours of data
as a minimum for good accuracy.  Additional hours will not yield much
improvement. </para>
    <para>The output will consist of one RINEX 3 observation file that
is ready to be read by your PPP program.  The default filename will be
in the form: gpsrinexYYYYJJJHHMMSS.obs.  You can override this filename
with the -f option.</para>
    <para>Optionally a server, TCP/IP port number and remote device can
be given.  If omitted, <application>gpsrinex</application> connects to
localhost on the default port (2947) and watches all devices opened by
<application>gpsd</application>.</para>
  </refsect1>
  <refsect1 id="options">
    <title>OPTIONS</title>
    <para>-D [debuglevel]  set debug level to [debuglevel].</para>
    <para>-f [filename] save RINEX into [filename].</para>
    <para>-h makes <application>gpsrinex</application> print
a usage message and exit.</para>
    <para>-i [interval] wait [interval] seconds between epochs.  OPUS
accepts intervals of 1, 2, 3, 5, 10, 15 or,30 seconds.  OPUS then
reduces the data to 30 second intervals.  Defeault is 30.</para>
    <para>-n [count] causes [count] epochs to be output.  OPUS requires a
minimum af 15 minutes, and a maximum of 48 hours, of data.</para>
    <para>-V makes <application>gpsrinex</application> print
its version and exit.</para>
  </refsect1>
  <refsect1 id="exampletitle">
    <title>EXAMPLES</title>
    <para>Example 1:</para>
    <para>Create a 4 hour .obs file.  With a running
<application>gpsd</application> accessible on the localhost do all of
the following, in order.  Order matters.</para>
    <para>The raw measurement messages are long.  Be sure your serial port
speed is high enough:
<programlisting>
gpsctl -s 115200
</programlisting></para>
    <para>Disable all NMEA messages, and enable binary messages:
<programlisting>
ubxtool -d NMEA
ubxtool -e BINARY
</programlisting></para>
    <para>The NEO-M8N will only reliably output raw measurements
when only the GPS and QZSS constellations are enabled.  If your PPP
service can use GLONASS, then enable that as well.  Be sure to 
disable, before enable, so as not to momentarily have too many
constellations selected.
<application>ubxtool</application>, as recommended by u-blox, enables
the QZSS constellation in tandem with GPS.  Disable all constellations,
except GPS (and QZSS):

<programlisting>
ubxtool -d BEIDOU
ubxtool -d GALILEO
ubxtool -d GLONASS
ubxtool -d SBAS
ubxtool -e GPS
</programlisting></para>
    <para>Verify the constellations enabled:
<programlisting>
ubxtool -p GNSS
</programlisting></para>
    <para>Enable the good stuff, the raw measurement messages:
<programlisting>
ubxtool -e RAWX
</programlisting></para>
    <para>Verify raw data messages are being sent:
<programlisting>
ubxtool | fgrep RAWX
</programlisting>
You should see this output:
<programlisting>
UBX-RXM-RAWX:
UBX-RXM-RAWX:
</programlisting></para>
    <para>Collect 4 hours of samples at 30 second intervals, save the
RINEX 3 observations in the file today.obs:
<programlisting>
gpsrinex -i 30 -n 480 -f today.obs
</programlisting></para>
    <para>Wait 4 hours.  Enjoy a meal, or do some exercise.  When 
<application>gpsrinex</application> finishes, upload the file today.obs
to your favorite PPP service.</para>
    <para>Example 2:</para>
    <para>Collect raw masurement data from a remote gpsd.  The
process it later with <application>gpsrinex</application> and
<application>gpsprof</application>.</para>
    <para>Ensure the GPS is configured properly, as shown in Example 1.</para>
    <para>Grab 4 hours of raw live data from remote
<application>gpsd</application> at 10.168.1.2:
<programlisting>
gpspipe -x 14400 -R 10.168.1.2 > 4h-raw.ubx
</programlisting></para>
    <para>When <application>gpspipe</application> is complete, feed the
data to <application>gpsfake</application>:
<programlisting>
gpsfake -1 -P 3000 4h-raw.ubx
</programlisting></para>
    <para>In another window, feed the data to 
<application>gpsrinex</application>.  Use -n 10000000 so that
all the data from the raw file is used::
<programlisting>
gpsrinex -i 30 -n 1000000
</programlisting></para>
    <para>Repeat the process with 
<application>gpsfake</application> to send the data to 
<application>gpsprof</application>.</para>
  </refsect1>
  <refsect1 id="see_also">
    <title>SEE ALSO</title>
    <para>One service known to work with obsrinex output is at:
https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php</para>
    <para>OPUS requires 2 frequency observation files.
https://www.ngs.noaa.gov/OPUS/</para>
    <para>The curious can find the RINEX 3.03 format described here:
ftp://igs.org/pub/data/format/rinex303_update1.pdf</para>
    <para>
      <citerefentry>
        <refentrytitle>gpsd</refentrytitle>
        <manvolnum>8</manvolnum>
      </citerefentry>,
<citerefentry><refentrytitle>gpsfake</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>ubxtool</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
</para>
  </refsect1>
  <refsect1 id="maintainer">
    <title>AUTHOR</title>
    <para>Gary E. Miller <email>gem@rellim.com</email>.</para>
  </refsect1>
</refentry>
